Tune gencache a bit

[Jeremy Allison]

On Tue, Nov 27, 2012 at 02:18:24PM +0100, Volker Lendecke wrote:
> On Fri, Nov 23, 2012 at 03:26:20PM +0100, Volker Lendecke wrote:
> > Hi!
> > 
> > Recently I came across a workload where we were writing the
> > same value into gencache over and over again. This led to a
> > significant slowdown due to the frequent transaction_commit
> > calls doing msync and fsync syscalls.
> > 
> > The attached patchset reduces this workload. We do not write
> > into the cache if we write the same value, extending the
> > remaining cache time by less than 10%.
> > 
> > Comments?
> 
> Attached find a new patchset with some comments of Christian
> Ambach taken care of.
> 
> Thanks,

Looks good to me. Pushed to autobuild.

Jeremy.